Modeling A Renewable Energy System That Relies on Biofuel Production Using Bacteria and Stores it through Chemical Storage Systems

— The need for bioenergy as a sustainable alternative to fossil fuels is increasing, and the production of biofuels using bacteria is considered one of the prominent methods used in this field. This research aims to model the process of producing biofuels using bacteria and storing them using a chemical storage system. A mathematical model was used to analyse the process, where the chemical constants and optimal environmental conditions for the process were determined. The process variables were identified, including acidity level, increased production coefficient, and the effect of thermal variables on the process. The productivity and efficiency of the process of producing biofuels using bacteria were analysed, and the effect of environmental variables on this process was studied. The produced biofuels were stored in a chemical storage system, where the system was analysed, and the appropriate conditions for safely storing biofuels were determined. The data resulting from the mathematical model and the storage system were analysed and graphed. The research concluded that biofuels can be efficiently produced using bacteria and safely stored using a chemical storage system. The effect of environmental variables was analysed, and the chemical constants used in the mathematical model were optimized, resulting in a significant improvement in the efficiency of the process. The results of this research can be used to improve the process of producing biofuels and develop safer and more efficient storage systems for biofuels.


I. INTRODUCTION 1
Renewable energy is considered one of the most important environmental and economic issues facing the world today.The increasing reliance on fossil fuels as an energy source leads to higher temperatures on the Earth's surface and increased carbon emissions, which cause serious climate changes and threaten global security.Therefore, investing in renewable energy and developing renewable energy systems is one of the main solutions to this problem [1].
Using biofuels is one of the main sources of renewable energy, and this can be achieved by producing biofuels using bacteria.Bacteria are microorganisms that can be used to convert various organic materials into biofuels, such as biogas, ethanol, and biodiesel [2].
For example, bacteria can be used in the process of converting sugars into ethanol, where they use fermentation to convert sugars found in organic materials into ethanol.Ethanol can be used as a biofuel to operate different engines and machines, reducing reliance on fossil fuels that cause pollution and climate change [3].
To store the produced biofuel, chemical storage systems such as batteries or fuel cells can be used.The biofuel is stored in the form of chemical energy and is converted into electrical energy that can be used in various fields [4].
The proposed model is based on these technologies, where bacteria are used to produce biofuels and are stored in the form of chemical energy using chemical storage systems.This model aims to develop a renewable energy system that relies on renewable and environmentally friendly sources and can be used as an alternative to the currently used fossil fuels.
In this model, bacteria convert various organic materials into biofuels, and chemical systems are used to store the produced biofuel.This biofuel is then converted into electrical energy that can be used to operate different engines and machines and can also be used to generate electricity using fuel cells.
Developing a renewable energy system like this model requires consideration of many technical, environmental, and economic aspects.For example, improving the efficiency of bacteria in producing biofuels and improving chemical storage systems to increase the efficiency of using biofuels and reduce costs must be considered.Environmental aspects must also be considered by reducing carbon emissions and environmental pollution and improving air and water quality.Economic aspects should also be considered by analyzing the cost and benefits and identifying the targeted markets for biofuels [5].
To achieve these goals, researchers and engineers must work on developing new techniques for producing biofuels using bacteria and improving the performance of chemical storage systems.Computer models that assist in analyzing the performance, efficiency, and cost of the proposed renewable energy system should also be developed.
The proposed model is an important step in achieving these goals, as it can be used as a model for developing sustainable and environmentally friendly renewable energy systems.This model can be applied in many fields, such as generating electricity and operating different vehicles and machines using the biofuel produced through this system.

II. LITERATURE REVIEW
Renewable energy is a critical issue facing the world today, as the continued reliance on fossil fuels leads to increased carbon emissions and serious climate changes.Biofuels Modeling A Renewable Energy System That Relies on Biofuel Production Using Bacteria and Stores it through Chemical Storage Systems Firas Lattef Hussany produced using bacteria offer a promising solution to this problem, as they are renewable and environmentally friendly.
In this literature review, we will examine the existing research and literature on the use of bacteria to produce biofuels and the storage of these biofuels using chemical storage systems.

A. Production of Biofuels Using Bacteria
Bacteria are microorganisms that can be used to convert various organic materials into biofuels, such as biogas, ethanol, and biodiesel.Wang et al. [6] conducted a review of the microbial production of biofuels and found that bacteria can be used to produce biofuels from lignocellulose biomass.Li et al. [7] also found that bacteria can be used to produce biofuels from various organic materials, and identified the need to improve the efficiency of bacteria in producing biofuels.
One of the main examples of using bacteria to produce biofuels is the process of converting sugars into ethanol using fermentation.Chisti [8] reviewed the use of microalgae to produce biofuels and highlighted the importance of using fermentation to produce ethanol from sugars found in organic materials.
Recent research has made significant progress in developing efficient and effective methods of producing biofuels using bacteria.Chen et al. [9] developed a novel strategy for producing biofuels using bacteria and waste biomass, using a combination of metabolic engineering and fermentation optimization to achieve high yields of biofuels from a range of waste materials.Another area of research has focused on the use of synthetic biology to develop bacteria that can produce biofuels from a wider range of organic materials.In 2023, Li et al. [10] reported on the development of a new strain of bacteria that can produce biofuels from lignin, a waste product of the paper industry, using a combination of genetic engineering and fermentation optimization to achieve high yields of biofuels from lignin.

B. Chemical Storage Systems for Biofuels
To store the produced biofuels, chemical storage systems such as batteries or fuel cells can be used.Demirbas [11] conducted a study on the production of biodiesel from vegetable oils using transesterification in supercritical methanol and found that chemical storage systems such as batteries can be used to store biodiesel.Additionally, Li et al. (2011) noted the importance of improving chemical storage systems to increase the efficiency of using biofuels and reduce costs.
The development of efficient and effective chemical storage systems for biofuels remains an important area of research in 2023.Recent advances in battery technology have led to the development of new types of batteries that can store higher amounts of energy and have longer lifetimes.Wang et al. [12] reported on the development of a new type of solidstate battery that can store biofuels with high efficiency and stability, using a combination of materials engineering and battery design optimization to achieve high performance.Other researchers have focused on the development of fuel cells for the storage of biofuels.Zhou et al. [13] reported on the development of a new type of fuel cell that can store biofuels with high efficiency and stability, using a combination of materials engineering and fuel cell design optimization to achieve high performance.

C. Considerations for Developing a Renewable Energy System
Developing a renewable energy system that relies on biofuels produced using bacteria and stored using chemical storage systems requires consideration of technical, environmental, and economic aspects.Improving the efficiency of bacteria in producing biofuels and improving chemical storage systems should be considered, as well as reducing carbon emissions and environmental pollution and improving air and water quality.Economic aspects should also be considered by analyzing costs and benefits and identifying the targeted markets for biofuels.Recent research has highlighted the importance of optimizing the efficiency of biofuel production and storage, as well as reducing the environmental impact of biofuel production and use.
For example, Li et al. [14] conducted a life cycle assessment of biofuels produced using bacteria and found that the environmental impact of biofuel production can be significantly reduced by optimizing fermentation conditions and using renewable sources of energy.They also noted the importance of developing a circular economy for biofuels, where waste materials can be used as feed stocks for biofuel production.
Moving forward, it will be critical to continue developing new techniques for producing biofuels using bacteria and improving the performance of chemical storage systems.Additionally, it will be important to consider the technical, environmental, and economic aspects of developing a renewable energy system that relies on biofuels produced using bacteria and stored using chemical storage systems.

III. PROCESS DESCRIPTION
The production of biofuels involves the use of bacteria.Specifically, the E. coli bacterial strain is utilized to produce biofuels through the fermentation of glucose, which generates ethanol and carbon dioxide.The fermentation process occurs within a chemical reactor, where various chemical process variables are monitored, including chemical compound concentration, biomass, gas pressure, storage temperature, and reaction-generated heat.Other variables, such as ambient temperature, air flow rate, surface area, storage volume, chemical compound density, specific heat capacity of the chemical compound, and the Stefan-Boltzmann constant, are also considered.
To calculate the various variables in the chemical process at each time step, a code is used.Differential equations are employed to determine growth rates and conversion rates, while heat loss and gain variables are calculated within the storage system.The results are presented through a graphical representation of the different variables.
The mass of biofuel produced and the total heat generated during the chemical process are also calculated.

A. Variables
When producing biofuels using bacteria, there are numerous variables that are simulated and analyzed for their impact on the system.

Temperature
Temperature is one of the primary factors that influence the process of producing biofuels.An increase in temperature accelerates the rate of conversion of glucose to ethanol and carbon dioxide.In practice, the temperature inside the chemical reactor is increased by heating the medium containing glucose and bacteria.

Gas Pressure
Gas pressure affects the process of converting glucose to ethanol and carbon dioxide.An increase in gas pressure inside the chemical reactor leads to an increase in the rate of conversion of glucose to ethanol and carbon dioxide.Therefore, gas pressure is increased inside the chemical reactor by compressing the gas inside the reactor.

Air Flow Rate
Air flow rate affects the process of converting glucose to ethanol and carbon dioxide.An increase in the air flow rate inside the chemical reactor leads to an increase in the rate of conversion of glucose to ethanol and carbon dioxide.Therefore, the air flow rate inside the chemical reactor is increased by supplying the reactor with a sufficient amount of oxygen.

Surface Area
Surface area is a crucial factor that affects the process of converting glucose to ethanol and carbon dioxide.An increase in surface area inside the chemical reactor improves the flow of glucose and bacteria inside the reactor, leading to an increase in the rate of conversion of glucose to ethanol and carbon dioxide.

Storage Volume
Storage volume affects the amount of biofuel that can be stored and thus affects production efficiency.A larger storage volume allows for larger amounts of biofuel to be stored, which improves production efficiency.Therefore, the storage system should be designed to be proportional to the total production volume.

Bacteria Type
The type of bacteria used in the process of producing biofuels affects production efficiency.For example, ethanol bacteria can be used to produce ethanol, but other bacteria, such as butanol bacteria, can also be used to produce butanol.The type of bacteria affects the conversion rate and production efficiency.

Glucose Type
The type of glucose used in the process of producing biofuels affects production efficiency.For example, corn glucose or regular sugar glucose can be used, and this type of glucose can affect the conversion rate and production efficiency.

Time Duration
The time required to produce biofuels affects production efficiency.A shorter production time leads to higher productivity.Therefore, the system should be designed to determine the optimal production time.
These variables are critical in the process of producing biofuels and are carefully monitored and analyzed to achieve the best system efficiency.Improvements in different variables can increase productivity and improve system efficiency.

B. Steps
The biofuel production process involves several steps and mathematical equations that determine different parameters of the process.Optimizing these parameters can enhance the efficiency of the process and increase yields of biofuel, which contributes to environmental and economic sustainability.
Firstly, bacteria convert sugars into ethanol, which is the primary mechanism of biofuel production.The efficiency of this process depends on the amount of ethanol produced compared to the amount of glucose consumed using the following equation: The process efficiency can be enhanced by optimizing the growth conditions for the bacteria, such as temperature, pH, and nutrient availability.Genetic engineering techniques can also be used to modify the bacteria and improve their efficiency in converting sugars to ethanol.The equation for calculating process efficiency is: Secondly, determining the conversion rate of glucose to ethanol is critical to assessing the efficiency of the process.The equation used to calculate this rate is: where V is the productivity rate of ethanol, k is the rate constant of the process, [S] is the concentration of sugars, and [X] is the cell density.The productivity rate of ethanol can be determined by measuring the amount of ethanol produced over a specific period of time.The rate constant of the process can be influenced by a variety of factors, including the type of bacteria used, the concentration of sugars, and the temperature and pH of the growth medium.Thirdly, calculating the cell growth rate is essential to determining the efficiency of the process.The equation used to calculate the cell growth rate is: where μ is the cell growth rate, X1 is the cell density at time t1, and X2 is the cell density at time t2.The cell growth rate can be influenced by the type of bacteria used, the nutrient availability, and the pH and temperature of the growth medium.
Fourthly, the energy efficiency of the biofuel production process is an essential parameter to assess the overall efficiency of the process.The equation used to calculate the energy efficiency is: The energy efficiency can be influenced by several factors, including the type of bacteria used, the concentration of sugars, and the temperature and pH of the growth medium.
Fifthly, determining the flow rate of biofuel produced during the process is crucial to assessing the efficiency of the process.The equation used to calculate the flow rate is: where Q is the flow rate, V is the volume of biofuel produced, and t is the time.The flow rate can be influenced by several factors, including the concentration of sugars, the type of bacteria used, and the temperature and pH of the growth medium.
Finally, gas pressure is a critical parameter to determine during the biofuel production process, as it can affect the efficiency and safety of the process.The partial pressure of a gas can be calculated using Dalton's law, which states that the partial pressure of a gas is equal to the total gas pressure × the gas concentration.The equation used to calculate gas pressure is: where   is the partial pressure of the gas,   is the total gas pressure, and   is the gas concentration.The gas pressure can be influenced by several factors, including the type of gas produced during the process, the type of bacteria used, and the temperature and pressure of the growth medium.
The change in chemical compound concentration is calculated at each time step using the formula: The change in chemical compound concentration is the result of the combination of the chemical compound dissolution (r1) and its consumption by bacteria (r2).

𝑆(𝑖) = 𝑆(𝑖 − 1) + 𝑑𝑆 × 𝑑𝑡
The concentration of the chemical compound in the current step (i) is calculated by adding the change in chemical compound concentration (dS) multiplied by time (dt) to the concentration of the chemical compound in the previous step (i-1).
The change in biomass mass is calculated at each time step using the formula: The change in biomass mass is the result of bacterial growth (r2).

𝑋(𝑖) = 𝑋(𝑖 − 1) + 𝑑𝑋 × 𝑑𝑡
The biomass mass in the current step (i) is calculated by adding the change in biomass mass (dX) multiplied by time (dt) to the biomass mass in the previous step (i-1).
Equation for calculating the change in biofuel concentration: The change in biofuel concentration is calculated at each time step using the formula: The change in biofuel concentration is the result of the biofuel formation reaction (r3).

𝑃(𝑖) = 𝑃(𝑖 − 1) + 𝑑𝑃 × 𝑑𝑡
The biofuel concentration in the current step (i) is calculated by adding the change in biofuel concentration (dP) multiplied by time (dt) to the biofuel concentration in the previous step (i-1).
Equation for calculating the change in temperature: The change in temperature is calculated at each time step using the formula: The change in temperature is the result of the biofuel formation reaction (r3) and heat transfer from the reactor to the environment.The change in temperature is calculated using density (rho), specific heat capacity (c), reactor volume (Vr), heat transfer coefficient (U), surface area (A), temperature in the previous step (T(i-1)), and external temperature (T_env).
In summary, the biofuel production process involves several steps and mathematical equations that determine various parameters of the process.Optimizing these parameters can enhance the efficiency of the process and increase yields of biofuel, contributing to environmental and economic sustainability.

IV. SYSTEM MODELING
To model the biofuel production system using bacteria and storing it in a chemical tank, the aforementioned equations were modeled, and the variables were initialized with initial values.The chemical variables used were organized in separate tables.Table I  The system processes were modeled using MATLAB.Since E. coli is the most common bacterium in fermentation processes, according to the previous study, it was relied upon to model the system.According to the previous study, E. coli is considered one of the main types of bacteria used in biofuel production.Therefore, it was chosen to model the system.

V. SIMULATION OF RESULTS
The results that are plotted and simulated represent detailed outcomes of the biofuel production and chemical storage process.These results include several variables that can be understood more widely, which include:

A. Chemical Compound Concentration (S)
Checmical compound concentration represents the concentration of the raw material used in the production process, which significantly affects the rate of the bioreaction and the conversion of the raw material into fuel.This variable is plotted on the X-axis in Fig. 1, showing how the concentration of the raw material changes over time.

B. Biomass Concentration (X)
Biomass concentration represents the biomass of bacteria used to convert the raw material into fuel.This variable is plotted on the Y-axis in Fig. 1, showing how the biomass concentration changes over time.

C. Fuel Concentration (P)
Fuel concentration represents the concentration of the fuel produced from the bio-reaction, which is considered the final product of the production process.This variable is plotted on the Y-axis in Fig. 1, showing how the fuel concentration increases over time.

D. Temperature (T)
Temperature indicates the temperature in the chemical system, which significantly affects the rate of the bio-reaction and the conversion of the raw material into fuel.This variable is plotted on the X-axis in Fig. 2, showing how the temperature changes in the chemical system over time.

E. Heat Flow (Q)
Heat flow represents the amount of heat added or supplied in the chemical system, which directly affects the temperature and the rate of the bio-reaction.This variable is plotted on the Y-axis in Fig. 2, showing how the heat flow changes in the chemical system over time.

F. Enthalpy (kJ)
Enthalpy represents the total energy stored in the chemical system, which is significantly affected by the temperature and the rate of the bio-reaction.This variable is plotted on the Yaxis in Fig. 3, showing how the enthalpy changes in the chemical system over time.

G. Reaction Rate (r)
Reaction rate represents the bio-reaction rate that occurs in the chemical system, which is significantly affected by the concentrations, temperature, heat flow, and enthalpy.This variable is plotted on the Y-axis in Fig. 4, showing how the reaction rate changes in the chemical system over time, where: -Variable r_H2_prod, which is plotted with the symbol "r1," represents the rate of hydrogen gas production and is plotted in dark red.-Variable r_CH4_prod, which is plotted with the symbol "r2," represents the rate of methane gas production and is plotted in dark green.-Variable r_CO2_prod, which is plotted with the symbol "r3," represents the rate of carbon dioxide gas production and is plotted in dark blue.

H. Concentration and Temperature Changes
Concentration and temperature changes represent how the concentrations of the materials S, X, P, and the temperature change during the chemical reaction over time, as shown in Fig. 5.

I. Stored Biofuel
Stored biofuel represents the amount of biofuel stored in the chemical tank, where the biofuel mass is represented in Fig. 6 as one kg, and the stored biofuel concentration is represented in Fig. 7 as one mM.
The simulation results show how different variables interact in the chemical process of producing biofuel using bacteria and storing it in a chemical tank.Initially, the required variables for simulating the chemical process are determined.Then, the simulation is run using a loop that calculates the values of the different variables at each time step.Through the simulation, we can monitor the interaction of the different variables over time.
For example, a change in the concentration of different chemical compounds over time can be observed.The effect of temperature on the rate of reactions can also be seen, as temperature usually increases the chemical process, and in turn, increases the rate of reactions.
In addition, the graphs show the interaction of the different variables over time.Changes in the concentration of different chemical compounds over time, changes in temperature, rate of reactions, and changes in the concentration of fuel in the storage tank can be seen over time.

A. Effects of Environmental Variables
This section reviews the study of the impact of environmental changes, where each of the ambient temperature, oxygen pressure, carbon dioxide pressure, and pH level were simulated.We will discuss in detail the effect of both carbon dioxide pressure and pH level while keeping the ambient temperature and oxygen pressure constant.

Effect of Carbon Dioxide Pressure on the Environment
In this section, we will examine how changes in carbon dioxide pressure affect the environment, particularly in terms of producing biofuels using bacteria and storing them in a chemical tank.Figs. 8 to 14 illustrate a simulation of the biofuel production and storage process under the condition that the ambient carbon dioxide pressure equals 0.01.As observed from the previous simulation, the production and storage of biofuels are negatively affected by carbon dioxide.Therefore, it is crucial to keep the concentration of carbon dioxide in the environment to a minimum level.To reflect more realistic values, the carbon dioxide pressure variable will be set to a value of 0.05.

Effect of pH Level in the Environment
This section aims to investigate how the pH level of the environment impacts the production and storage of biofuels.The simulation process will be conducted in both neutral and acidic environments, as it had previously been conducted solely in a neutral environment in the preceding sections.From the previous simulation, it was observed that an acidic environment negatively affects the production and storage of biofuels, whereas a neutral or basic environment has a lesser impact on the process.Hence, maintaining a neutral or basic environment during the process is crucial.The results suggest that a relatively neutral pH value is optimal for the process.Therefore, the pH value will be maintained at a constant value of 7 in subsequent experiments.

B. Effect of Variables Related to the Chemical Process
To ensure the efficiency of the chemical process and achieve the highest rate of fuel production, several important variables must be calibrated and adjusted.

Michaelis Constant
Optimizing the enzyme reaction and increasing the fuel production rate requires adjusting the Michaelis constant (km), which controls the rate of the enzyme reaction with the chemical compound that is being converted into fuel.
When the Michaelis constant is adjusted to a value of 0.1, Figs.36-42 demonstrate the simulation results of the process.
When the Michaelis constant is adjusted to a value of 5, Figs.43-49 demonstrate the simulation results of the process.Based on the previous simulation, we noticed that low values of the Michaelis constant result in extreme values of process performance with low flow rates but high speed.On the other hand, high values of the constant result in a decrease in the chemical reaction speed but provide high flow rates that are closer to real-world operations.Therefore, to maintain the required speed and flow rate similar to real-world operations, the constant needs to be adjusted to a moderate value.Consequently, the constant will be adjusted to a value of 1.

Yield Coefficient
To achieve the highest fuel production rate, the yield coefficient value must be adjusted.The yield coefficient (Y) denotes the proportion of produced fuel to the amount of the chemical compound being converted.When the yield coefficient (Y) is adjusted to a value of 1, Figs. 50-56 display the simulation results of the process.

Reaction Rate Constant
The speed of the conversion reaction is expressed by the reaction rate constant (k), which needs to be adjusted to achieve the highest rate of fuel production.Results of simulating the system when the reaction rate constant is set to 0.1 are shown in Figs.57-63, while Figs.63-70 display the results when the reaction rate constant is set to 10.
Based on the previous findings, it is evident that low values of the reaction rate constant have a negative impact on the reaction rate, while extremely high values can result in unrealistic outcomes.Thus, the reaction rate constant was modified to ensure optimal system performance and speed.These simulation results offer valuable insights into the behavior of the chemical process and can be utilized to optimize the process parameters for enhanced performance.The discussion of the findings indicates that several variables require consideration, such as the Enzyme Kinetics Constant (Km), which controls the rate of enzyme reaction with the chemical compound that is transformed into fuel.Adjusting the Km value can lead to an optimal enzyme reaction and an increase in the rate of fuel production.The Yield Coefficient (Y) represents the ratio of fuel produced in relation to the amount of chemical compound converted.Adjusting the Yield Coefficient value can result in the highest rate of fuel production.Finally, the Reaction Rate Constant (k) represents the rate of conversion reaction, and adjusting this value can result in the highest rate of fuel production.

VIII. CONCLUSION
The study focuses on the process of producing biofuel using bacteria and storing it in a chemical tank, and a simulation of this process was conducted using various different variables.The behavior of the chemical process was illustrated through the presented figures, which included the concentrations of the chemical compound, biomass, and biofuel, the system temperature and heat flow, the enthalpy content of the process, the reaction rates of the chemical reactions involved in the process, the changes in concentrations and temperature, and the results of the storage tank, including the mass of biofuel and the biofuel concentration.
The results were analyzed and the different variables and their effects on the chemical process were discussed.The results showed that controlling some key variables such as the Enzyme Kinetics Constant (Km), Yield Coefficient (Y), and Reaction Rate Constant (k) can improve process performance and increase the rate of fuel production.
It was concluded that the results of this study can be used
Fig.s 22-28 illustrate the simulation of the system in an acidic medium.Figs.29-35 illustrate the simulation of the system in a neutral medium.
represents the chemical variables, Table II represents the Environmental variables, and Table III represents the Time variables.